Allulose is a “zero-calorie” sweetener and has sweetness suggested to be similar to dextrose. It also has bulking and browning properties similar to those of other sugars. The primary target market for allulose is food and beverage manufacturers that currently use dextrose, fructose or HFCS in their products and that are looking to significantly reduce calories without significantly altering other properties imparted by the sugar component, for example, bulking, browning, texture and sweetness.
Allulose is not Generally Regarded As Safe (GRAS) in the United States but there is currently a GRAS notice pending (GRN400). Allulose is present in processed cane and beet molasses, steam treated coffee, wheat plant products and high fructose corn syrup. The typical total daily intake of allulose has been estimated to be greater than 0.2 grams per day. D-allulose is the C-3 epimer of D-fructose, and the structural difference between allulose and fructose results in allulose not being metabolized by the human body and thus having zero calories. Therefore, allulose is thought to be a promising candidate as a sweet bulking agent as it has no calories and is reported to be sweet while maintaining similar properties to typical monosaccharides.
Ketose-3-epimerases can interconvert fructose and allulose. U.S. Pat. No. 8,030,035 and PCT publication no. WO2011/040708 disclose that D-psicose (an alternative name for allulose) can be produced by reacting a protein derived from Agrobacterium tumefaciens, and having psicose 3-epimerase activity, with D-fructose.
US patent publication no. 2011/0275138 discloses a ketose 3-epimerase derived from a microorganism of the Rhizobium genus. This protein shows a high specificity to D- or L-ketopentose and D- or L-ketohexose, and especially to D-fructose and D-psicose. This document also discloses a process for producing ketoses by using the protein.
Korean patent no. 100832339 discloses a Sinorhizobium YB-58 strain which is capable of converting fructose into psicose (i.e. allulose), and a method of producing psicose using a fungus body of the Sinorhizobium YB-58 strain.
Korean patent application no. 1020090098938 discloses a method of producing psicose using E. coli wherein the E. coli expresses a polynucleotide encoding a psicose 3-epimerase.
The present invention seeks to provide an improvement in the production of allulose over existing technology. The present invention seeks to provide a ketose-3-epimerase with higher rates of conversion and volumetric productivity in a whole cell system than previously reported.